Re: Designing with Databases - Best Practice Class Hierachy?


"NC" <nc@xxxxxxxxx> wrote in message
news:1151278996.694450.283930@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
LiveFreeAndRoam wrote:

------------------------------------------------
class DataAccess extends MDB2 {
// DataAccess properties and methods
var $db;
function __construct($dsn) {
$this->db =& MDB2::factory($dsn);
}
}

class Table {
// table properties and methods
var $dao;
function __construct() {
$this->dao = new DataAccess(); // <<< OK?
}
}

class Product extends Table {
// Product properties and methods
}
--------------------------------------------------

One issue I have noticed is that when I attempt to recover
the Product Object from the $_SESSION superglobal that
the DataAccess object is unusable. MDB2 complains with:

MDB2 Error: not found: could not find MDB2 instance

Try calling parent::__construct() explicitly within
DataAccess::__construct():

class DataAccess extends MDB2 {
// DataAccess properties and methods
var $db;
function __construct($dsn) {
parent::__construct(); // Are there required parameters?
//
-------------------------------------------------------------------
// Now DataAccess has all properties and methods
// of MDB2, including the factory() method, so you
// can call the factory() method directly:
$this->db =$this->factory($dsn);
}
}

Is there a better way to design this?

Design has to achieve certain objectives. Since you didn't state your
objectives, no one can offer you an informed guess as to what other
design would be better to achieve those objectives...

Cheers,
NC


Thankyou NC.

In terms of objectives I would prefer to not have to do the following to
recover my DataAccess object to a state where it can be used:

$sessprod = unserialize($_SESSION['product']);
$product = new Product();
$product->setProperties($sessprod->getPropertiesExcludingDao());
$product->query($query);

I would prefer to simply do this:

$product = unserialize($_SESSION['product']);
$product->query($query);

Though, this isn't working for me as previously stated. I wondered whether
designing my class hierachies differently would allow me to achieve this
end.

Best Regards,
LFaR.


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